The mother of a baby killed in a crash involving an off-duty police officer has been charged with negligent homicide after authorities say she failed to properly secure her daughter in the car seat. Police arrested 20-year-old Brittany Stephens on Tuesday after determining her child’s car seat wasn’t properly secured and the straps were not correctly adjusted for her daughter’s height, according to an arrest report obtained by The Advocate. A Baton Rouge officer was arrested on the same charge after slamming into Stephen’s car at 94 MPH on the night of Oct. 12, killing her daughter and injuring several others.